Time-assignment speech-interpolation control system

ABSTRACT

A TASI system for satellite use is disclosed in which voice signals from the individual trunks are stored prior to being transmitted and in which TASI control data are transmitted in a frame preceding the frame in which associated speech data are transmitted.

United States Paten Amano et al.

[54] TIME-ASSIGNMENT SPEECH- 3,042,752 7/1962 INTERPOLATION CONTROL SYSTEM 7 ki ay 1 lnvemorfi Kilsumro Ammo, Yokohama-sh Chuichl 3,311,707 3/1967 rquhart-Pullen ..l79/l5 AS Ota,Tokyo; Masaol-lashimoto, Kanagawar r ken; Him z t igry 3 3 m OTHER PUBLICATIONS Sakamoto, awas I-s o uy ymhima, Tokyo, n f Japan Proceedings IEEE, Vol. III, No. 4, pp. 675- 684, Time Assignment Speech lnterpolatlon In TIme- CompressIon Mul- [73] Asslgnee: Fulltsu Kawasaki Japan tiplier Transmission," Author: Flood et al. [22] Filed: Sept. 19, 1969 '**"E*x' H Claff Primary aminera een y [21] Appl' 859285 Assistant ExaminerDavid L. Stewart Attorney-Curt M. Avery, Arthur E. Wilfond, Herbert L. [30] Foreign Application Priority Data Lerner and Daniel J. Tick Sept. 25, 1968 Japan ..43/69607 [57] ABSTRACT [52] U.S.Cl. ..l79/l5 AS A TASl system for satellite use is disclosed in which voice [51] lnt.Cl. ..H04j 5/00 signals from the individual trunks are stored prior to being [58] Field of Search 179/15 AS transmitted and in which TASl control data are transmitted in a frame preceding the frame in which associated speech data [56] References Cited are transmitted.

UNITED STATES PATENTS 7 Claims, 15 Drawing Figures 2,920,143 1/1960 Filipowsky l 79/15 AS SATELLITE 5 STATION A STATION B I A A VOICE INFORMATION 'I/QICE INFORMATION ,JL M BL'Q i' 2@ TRUN Ks SUBSCRIBERS TRUNKS H I l 1 15a X- l I -X/ 25 u 15bl\x I l rX -25b P n P n I 17-2 mm I 15| /X" I I l I X -25 S I I l l PCM EXCH A N G E p c M I I I I EOUIPMENT16 MODULATOR i I I g l IIDEMOGDCEJLATOR 18 L- I L... EXCHANGE i II I I EQUIPMENTiG I I A a c I Ann I l I s f? I I l as: I I i I I I I I I I L l L l CHANNEL CI-IANNEI. CONDITION CONDITION MEMORY 8 MEMORY 58 1 Feb. 22, 1972 Fulmer ..l79/l5 AS mm rmofwi w rmOEwE PAIENTEDFEB22 I922 SHEET UF .6

- voIcE INFORMATION FIB MEMORY1O BUFFER BUFFER REGI TER1I REGIsTER 9- I I r A A 7 2 BUFFER I REGISTER'4 I.

w T FTRASi GATE CONTROL IN 0 MATION LEVEL DIscRIMINAT R 5 A A ADDING g CIR1CZUIT- CIRCUITB QRITI G 3 READIN N BUFFER BUFFER REGISTER REGISTER 6 7 D A B c \CHANNEL CONDITION MEMORY B FIG .9 SF TIME D-sT A B c A a c sGT-sT c A B A SP-ST B c A B A I Q I I III IV I V VI PATENTDFEII22 I972 FIG.8

BUFFER REGISTER 9 CIRCFIT ITASI INFORMAT [ADDING CIRCUIT13 BUFFER REGISTER 4 LEVELCOMPARING I CIRCUIT 5a\ %0 N T 0 I LINc I I L I GATECONTROL ,cmcumz COUNTING I cIRcuIT5 i I .,TASI ALLOTTING II 1 K CIRCUITS'd I I I I -TIME CONTROL] I I I I WRITING READING BUFFER RE I S I E R REGISTERS 7 I 0 ABC CHANNEL CONDITION MEMORY B LEVEL DISCRIMINATOR 5 PAIENTEDFEII22 I972 READING BUFFER MEMORY 54 DISCRIMINATOR 57w SGR-ST SP-ST SHEET 6 BF 6 vOICE INFORMATION MEMORY 53 FIG 1 WRITING BUFFER MEMORY52 GATE CONTROL CIRCUIT 56 SEPARATING AND COMPILING CIRCUIT 55 r I II CHANNEL CONDITION -MEMORY58 FIG ii TIME F E F E F E F E F E 11 I11 DZ v v.1

TIME-ASSIGNMENTSPEECH-INTERPOLATION CONTROL SYSTEM DESCRIPTION OF THE INVENTION The present invention relates to a time-assignment speechinterpolation control system. More particularly, our invention relates to a control system in a communicationsystem utilizing a time-division multiplexing multiple-access system part or all of which utilizes a time-assignment speech-interpolation control system.

A time-assignment speech-interpolation system is hereinafter referred to as a TASI system. A TASI system is a control system, which, due to the fact that in a multiplex communication system talk or voice signals are often broken or interrupted, enables other voice signals to be transmitted during the idle time created by the breaking or interruption of the voice signals and utilizes the channels in accordance with the principle of time division to reduce the number of channels utilized. The high cost of channels of communication systems, such as satellite communication systems and submarine cable communication systems, may be effectively reduced by the utilization or application of the TASI control system. For this reason, efficiency of utilization of channels has heretofore been increased due to the utilization of the TASI system when voice is transmitted via expensive long-distance telephone channels. In the prior art, frequency-division multiplex channels are main channels to which the TASI system may be applied and pulse-amplitude modulation systems are chiefly applied to the part wherein there is switching operation of the.

TASI control system. In accordance with the development of the pulse-code modulation system, however, such PCM system has become active and PCM international channels are utilized and it is possible to now utilize TASI control on the PCM level.

In the TASI system, switching is essentially required at high speed, since channels are switched in accordance with the condition of the voice signals of a call which is in duration. For this reason, switching is at electronic speeds without regard to channels whose efficiency of utilization must be increased. When the channels are an analog system, itis generally required to provide a modulating and demodulating device for the switching operation. In the case of PCM channels, however, a modulating and demodulating device is not required, so that a PCM system is more economical than an analog system. When the signals are coded, however, there is generally a tendency for the required magnitude or capacity of the memory or storage to become enormous, and in aPCM TASI system the magnitude of the memory is an extremely important element affecting the cost of the system.

The principal object of our invention is to provide a new and improved time-assignment speech-interpolation control system.

An object of the invention is to provide a' TASI control system which utilizes a minimu memory capacity.

In the application of a TASLsys'tem, it is necessary to transmit informations representing the corresponding relationship between a channel device or trunk and the TASI channel or informations representing the modification of the corresponding relationship, that is, the TASI informations, besides the voice informations. There is, however, a considerable magnitude of TASI informations. Therefore, if the TASI informations and the voice informations are transmitted within a constant period of time, the voice informations are limited and it is impossible to transmit a large magnitude of voice informations.

An object of the invention is to provide a TASI control system which permits the transmission of a large magnitude of voice informations.

An object of the invention is to provide a TASI control system which transmits a large magnitude of voice informations and which comprises an extremely inexpensive structure.

An object of our invention is to provide a TASI system which functions with efficiency, effectiveness and reliability.

In accordance with the invention, a time-assignment speech-interpolation control system has a transmitter comprising a discriminator for determining the voice condition of each trunk of a voice communication system by determining if the voice condition transmitted via each trunk exceeds a specific level and allotting a time-assignment speech-interpolation system channel to such trunk. An input connected to the discriminator supplies thereto the trunks of a voice communication system having a plurality of trunks. A channel condition memory coupled tothe discriminator records timeassignement speech-interpolation informations indicating the corresponding relationship between trunks and time-assignment speech-interpolation channels determined by the discriminator. A voice information memory coupled to the discriminator and the input stores voice informations from the trunks to which time-assignment speech-interpolation channels are allotted from the voice informations in the order of the time-assignment speech-interpolation channels in accordance with the time-assignment speech-interpolation informations stored in the channel condition memory. A time-assignment speech-interpolation information-adding circuit connected to the. discriminator adds time-assignment speechinterpolation informations stored in the channel condition memory to voice informations stored in the voice information memory and transmits the informations. The channel condition memory includes a memory for storing the time-assignment speech-interpolationinformations controlling the voice informations being transmitted, a memory for storing the time-assignment speech-interpolation informations transmitted by being added to the voice informations and a memory for storing the time-assignment speech-interpolation informations in rewriting condition.

The time-assignment speech-interpolation control system further comprises means for dividing the time-assignment speech-interpolation informations into a plurality of frames and transmitting'the divided informations. Each of the memories of the channel condition memory stores addresses corresponding to the trunks and'each of the addresses comprises one bit.

The time-assignment speech-interpolation control system further comprises means for converting the time-assignment speech-interpolation informations to an information train of binary signals indicating if the time-assignment speech-interpolation channels are allotted to hit positions corresponding tothe trunks and transmittingthe'binary signals.

The time-assignment speech-interpolation control system further comprises a receiver having a separating and compil ing circuit for deriving time-assignment speech-interpolation informations from a received burst. An input connected to the separating and'compiling circuit supplies a received burst to the separating and compiling circuit. A voice information memory coupled to the input stores voice informations directed to the receiver. A channel'condition memory coupled to the separating andcornpiling circuit and to the voice information memory stores time-assignment speech-interpolation informations'provided by the separating and compiling circuit to read out the voice informations stored in the voice information memory corresponding to the trunks. The channel condi tion memory includes a pair of memories each of which is alternately utilizedas a memory for storing the time-assignment speech-interpolation informations for controlling the voice informations being read out and a memory for storing the timeassignment speech-interpolation infonnations being transmitted to the receiver.

Each of the pair of memories of the channel condition memory has addresses corresponding to the trunks and each of the addresses comprises one bit.

In order that our invention may be readily carried into effect, it will now be described with reference to the accompanying drawings, wherein:

FIG. 1 is a block diagram illustrating asatellite'communication system;

FIG. 2 illustrates a burst train of a satellite communication system;

FIG. 3 illustrates a burst of the burst train of FIG. 2;

FIG. 4 is a block diagram of an embodiment of the time-assignment speech-interpolation control system of our invention;

FIG. 5 is a block diagram of another embodiment of the time-assignment speech-interpolation control system of the invention;

FIGS. 6a, 6b, 6c, 6d and 6e illustratethe time relations of various informations;

FIG. 7 is a block diagram of an embodiment of the transmitter of FIG. 4;

FIG. 8 is a block diagram of an embodiment of the discriminator of FIG. 4;

FIG. 9 illustrates the operation of the channel condition memory of the transmitter;

FIG. 10 is a block diagram of an embodiment of the receiver of FIG. 4; and

FIG. 11 illustrates the operation of the channel condition memory of the receiver.

Although the TASI system of our invention is described with reference to a satellite communication system, the invention may be applied to any suitable communication system such as, for example, a submarine cable communication system, or the like.

In the figures, the same components are identified by the same reference numerals.

FIG. 1 illustrates a satellite communication system comprising a communication satellite S in space and N ground stations A, B, N. Bursts Bl, B2, BN are radiated from the ground stations A, B, N, respectively, at corresponding regulated times. The bursts are relayed by the communication satellite S and are received by each ground station.

FIG. 2 illustrates a burst train which comprises a burst Bl radiated from the ground station A at time [I and a burst BN radiated from the ground station N at time tN, so that the bursts are not mutually overlapping on the satellite. Furthermore, the bursts are repeatedly radiated at a sampling period T of the time division system. The repetition is referred to as a frame.

Each burst, as shown in FIG. 3, comprises voice information CH and control information P. Part of the control information comprises the TASI information T5. The TASI information TS is transmitted as part of the control information P.

The TASI information transmission system may be divided into a system in which the TASI information is provided as an information train indicating whether or not the trunks are allotted to the channels and a system in which the TASI information indicates only the content of change of the corresponding relation between the trunks and the channels. The first-mentioned system is known as a condition or state signal system and the last-mentioned system is known as a change signal system. The condition signal system may be divided into a system in which the condition of allotment of the trunks to the channels is transmitted in one frame and a system wherein said condition is divided into a plurality of parts which are transmitted in a plurality of frames.

Each of the two systems into which the condition signal system may be divided may be further divided into a system wherein'the same condition signal is transmitted only once and a system wherein the same condition signal is transmitted a number of times. The last-mentioned system may be further divided into a system wherein the signal is transmitted by adding a parity check code or error-correcting code thereto, the correct information being discriminated and regenerated from this at the receiver and utilized as an effective TASI signal and a system wherein the same information is transmitted an odd number of times and the receiver, in accordance with the logic of decision by majority, obtains effective TASI information with the greatest number of informations.

The system in which the same condition signal is transmitted only once includes a system wherein an additional code or error-correcting code is added to the condition signal. The change signal system -may also be divided into a system wherein the information concerning the change of corresponding relation between the trunks and the channel is transmitted in a frame and a system wherein said information is divided into a plurality of parts which are transmitted in a plurality of frames, and each of these systems may be divided into a system wherein the change signal is transmitted once and a system wherein said signal is transmitted a number of times.

Our invention may adopt the aforedescribed various signals in the TASI information-transmitting system. However, an embodiment of the invention is hereinafter described in which the condition signal type is adopted as the signal type, TASI information is divided into a plurality of frames and an errorcorrecting code is added in the transmission.

FIG. 4 illustrates an embodiment of the TASI system of the invention. In FIG. 4, in order to maintain the clarity of illustration, communication between two ground stations A and B is illustrated. That is, voice informations from ground station A are all directed to ground station B. In FIG. 4, a plurality of subscribers 15a, 15b, l5i are provided at the station A and a plurality of subscribers 25a, 25b, 25 are provided at the station B. A plurality of trunks l7-l, 17-2, l7-m are provided at the station A and a plurality of trunks 27-1, 27-2, 27-m are provided at the station B. There are thus m trunks at each station. There is mutual correspondence between the trunks l7-l and 27-l, 17-2 and 27-2, and 17-m and 27-m. There is no connection between or possible for connecting the trunks 17-l and 27-2 or 17-2 and 27-m.

The subscribers 15a, 15b, 151', 25a, 25b, 25 and the corresponding trunks 17-1, 17-2, 17-m, and 27-1, 27-2, 27-m are connected via exchange equipment 16 in accordance with arbitrary switching combinations. A PCM modulator 18 provides PCM modulation and time-multiplexes the voice informations from the trunks. The PCM modulator 18 may comprise any suitable known circuit. A voice information memory 10 is connected to the output of the PCM modulator l8 and functions to rearrange information having addresses of a number equal to the number of TASI channels, that is, n addresses. The voice information memory 10 comprises core memories, magnetic thin film memories, lC memories, or the like, and the operation of said voice information memory is described hereinafter. A channel condition memory 8 is connected to the voice information memory 10. The channel condition memory 8 comprises three sets of channel condition memories each having a number of addresses equal to the number of trunks 17-1, 17-2, 17m, that is, m addresses. The channel condition memory 8 stores information as to whether or not the TASI channel is allotted to each trunk. The channel condition memory 8 may comprise any suitable core memories, magnetic thin film memories, lC memories, or the like. The operation of the channel condition memory 8 is hereinafter described.

At station B, a voice information memory 53 functions to rearrange information and has addresses equal in number to the TASI channels, that is, n addresses. The voice information memory 53 comprises any suitable core memories, magnetic thin film memories, IC memories, or the like. The operation of the voice memory 53 is hereinafter described. A channel con dition memory 58 is connected to the voice information memory 53 and comprises two channel condition memories having addresses equal in number to the trunks 27-1, 27-2, 27-m, that is, m addresses. The channel condition memory 58 records whether or not the TASI channel is allotted to each trunk. The channel condition memory 58 may comprise any suitable core memories, magnetic thin film memories, IC memories, or the like. The operation of the channel condition memory 58 is hereinafter described. A PCM demodulator 60 is connected to the output of the voice information memory 53. The PCM demodulator 60 functions to demodulate and space divide the PCM time-multiplex signals and may constitute any suitable known circuitry. The PCM demodulator 60 is coupled to the subscribers 25a, 25b, 25] via the plurality of corresponding trunks 27-1, 27-2, 27-m and the exchange equipment 16.

In the embodiment of FIG. 4, voice informations are transmitted from m trunks l7-l, 17-2, l7-m at the station A to the corresponding m trunks 27-1, 27-2, 27-m at the station B. The transmission is achieved via n TASI channels, m being greater than n. Where there is communication between more than two stations A, B, N, our invention may be carried into effect by the embodiment of FIG. 5.

In the embodiment of FIG. 5, there is mutual correspondence between the trunk l7-l of the station A and the trunk 27-] of the station E, the trunk 17-2 of the station A and the trunk 27-2 of the station E, and the trunk 17-m of the station A and the trunk 97-1 of the station N. Furthermore, there is mutual correspondence between the trunk 97-m of the station N and a trunk of another station, not shown in the drawing.

Of n TASI channels allotted to the station A, p channels are directed to the station E and q channels are directed to the station N. Similarly, part of the TASI channels allotted to each of the station B and the station N is directed to the station A and the other part is directed to either the station N or the station B. By dividing the trunks of each station and the TASI channels allotted thereto into a plurality of parts and directing them to the other stations, as hereinbefore described, it becomes possible to utilize a system similar to that described with relation to FIG. 4, as hereinafter disclosed in greater detail.

In order to describe the system of FIG. 4 in detail, the information train or burst transmitted from the PCM modulator l8 and the information train or burst Bl transmitted to the station B are described with reference to FIGS. 6a, 6b, 6c, 6d and 6e. FIG. 6a shows a PCM signal train of trunks 17-1, 17-2, l7-m sampled and coded in synchronism with the frame-timing signals by the PCM modulator 18. FIG. 6a shows that the informations of the trunks 17-1, 17-2, l7-m are in the trunks TRKl, TRK2, TRKm, respectively. FIG. 6b illustrates whether each of the trunks of FIG. 6a is in speech condition S or pose condition P. TASI channels are allotted only to the trunks which are in the speech condition.

TASI channels allotted to the trunks which are in the speech condition are transmitted as a series in the order of said trunks. Therefore, the information train of FIG. 6a from the PCM modulator 18 is, as shown in FIG. 60, based upon FIG. 6b, and is transmitted to the station B. In FIG. 6c, TS is a part of the TASI control signal. A TASI control signal comprises a plurality of parts TS of the burst B1 of a plurality of frames, referred to as the signal frames SF, as shown in FIG. 6d. Thus, the TASI channels are preferentially allotted to the trunks in the speech condition and the information concerning such allotment is transmitted to the other station by the TASI control signal, which control signal is constituted by the parts TS of the burst Bl ofa plurality of frames.

The transmitter and receiver for transmitting and receiving the aforedescribed information are described with reference to FIGS. 7 and 10. FIG. 7 includes the voice information memory and the channel condition memory 8 ofthe station A of FIG. 4, and circuits related thereto. In FIG. 7, PCM signals 1 are provided by the PCM modulator 18 (not shown in FIG. 7). PCM signals 2 are transmitted to the station B via the communication satellite S. Timing control signals 3 comprise, for example, the frame timing representing the start and end of a sampling period.

The signals 1 are PCM signals which are compressed by the TASI control signal forming parts 4, 5, 6, 7 and 8. Regardless of whether the trunks 17-1, 17-2, 17-m are in the talking, voice or speech condition or in the nontalking or pose condition, PCM signals coded in correspondence with the signal levels are included in the signals 1. The signals 2 are PCM signals which have been compressed by the TASI control signal forming parts, and PCM signals corresponding to trunks which are in the speech condition are, as shown in FIG. 6c, transmitted in series in their order of arrival.

In FIG. 7, a buffer register 4 stores the PCM modulated signals of one trunk once. The information stored in the buffer register 4 is scanned or searched each time by a level discriminator 5 connected to said buffer register. The level discriminator 5 determines whether the signal from the trunk exceeds the designated level and determines whether the trunk is in the speech condition or pose condition. The TASI channel is allotted in accordance with such determination and the information is transmitted to other circuits requiring same.

In order that the discriminator 5 completely determine the condition of the trunks, it is necessary that the trunks be'supervised over several frames, so that a considerably long period of time is required. If the discriminator 5 is occupied by a single trunk during this period of time, the communication will be obstructed so that, in the invention, the channel condition memory 8 is provided. The condition of each trunk is written or read into the channel condition memory 8 in each frame and the written information is read out in the next frame and the new information so provided in the frame is added. It thus becomes possible to determine the condition of all the trunks.

Speech informations of the trunks l7-l, 17-2, l7-m are all transmitted from the PCM modulator 18 within one time division period, that is, one frame period. Therefore, voice informations are stored in and read out of the buffer register 4 the same number of times as the number of all the trunks within one frame period. A writing buffer register 7 writes from the discriminator 5 into the channel condition memory 8. A reading buffer register 7 reads from the channel condition memory 8 to the discriminator 5.

The voice information memory 10 rearranges information in which only the voice informations ofthe trunks to which the TASI channels have been allotted are stored via a buffer register 9. The writing of information into the voice information memory 10 is controlled by a gate control circuit 12. The information is read out to a buffer register 11 under the control of the gate control circuit 12. An error correcting code is added to the information by a TASI control signal adding circuit 13. After the transmission of the TASI control signals, informations stored in the voice information memory 10 are transmitted in succession via the buffer register I].

The writing into and readout of voice information memory 10 of FIG. 7 is described in detail with reference to FIGS. 6a to 6e. Voice informations of all the trunks l7-l, 17-2, l7-m are transmitted from the PCM modulator 18 to the buffer register 9 of FIG. 7 in the pattern shown in FIG. 6a regardless of whether each trunk is in the speech condition or the pose condition. As hereinafter described, however, information as to whether or not the TASI channel is allotted to each trunk is stored in the channel condition memory 8 of FIG. 7, and the gate control circuit 12 provides a suitable control based upon the information from the channel condition memory 8. Thus, only the voice informations of the trunks to which TASI channels have been allotted from the voice informations stored once in the buffer register 9 may be written in succession in the addresses l-n of the voice information memory 10 in the order of their arrival (FIG. 7

There is mutual correspondence between the addresses of the voice information memory 10 and the TASI channels. The address 1 corresponds to the TASI channel 1, which is CH1, and the address n corresponds to the TASI channel n, which is CI-In. Voice informations are read out from the voice information memory 10 in the following manner. If voice informations are read out in succession from the address 1 of the voice information memory 10, the readout information train is that shown in FIG. 60, and only the voice informations of trunks to which TASI channels have been allotted are transmitted to the station B. At this time, TASI informations are added by the TASI information-adding circuit 13 in the form of the information train of FIG. 6e and are transmitted. That is, the TASI informations are transmitted as an information train of binary signals 1" and 0 indicating whether or not the TASI channels are allotted to the bit positions corresponding to the trunks, as shown in FIG. 6e.

The capacity of the voice information memory 10 may thus be reduced, in accordance with our invention, by storing only the voice informations of trunks to which TASI channels have been allotted and by not storing voice informations of trunks to which TASI channels have not been allotted.

In FIG. 7, the gate control circuit 12 controls the writing into the voice information memory 10 under the control of the TASI information-forming part and controls a series of reading operations via the timing control signals 3. The TASI information-forming part comprises the buffer register 4 in which PCM signals are stored once, the level discriminator 5, the channel condition memory 8, the writing buffer register 7 and the reading buffer register 6. The circuits 4, 5, 6, 7 and 8 all function synchronously with the timing control signals 3.

The discriminator 5 determines whether or not PCM signals of one voice information stored in the buffer register 4 exceed the designated level. If the designated level is exceeded, there is a possibility that the trunk is in the speech condition, whereas if said designated level is not exceeded, there is a possibility that the trunk is in the pose condition. Only the possibility may be determined, since it is difficult, due to noise and the like, to instantaneously determine whether or not the speech condition or the pose condition is present. The counting of the duration time of the speech level or condition is therefore indicated in the positivedirection and the counting of the duration time of the pose level or condition is indicated in the negative direction. The counting of the two directions is performed for each trunk.

Counting is performed once in each frame for a trunk. Since the discriminator 5 is required to perform such counting for a plurality of trunks in a frame, the counting result is immediately recorded in a D part of the address (FIG. 7) corresponding exclusively to the trunk in the channel condition memory 8. If it is determined that a PCM signal corresponding to a specific trunk in a specific frame is in the speech level or condition, +2n is added to the D part of the corresponding address. If it is determined that the PCM signal is in the pose level or condition, 1 is subtracted from the D part of the corresponding address. In this instance n may be a suitable positive integral value corresponding to the degree of necessity for reducing the delay of time for determining the speech condition.

If the result provided by providing addition of subtraction, as hereinbefore described, exceeds a specific value, it is concluded that the trunk is in the speech condition. If the result is less than a specific value, it is concluded that the trunk is in the pose condition. A TASI channel is allotted to the trunk which is in the speech condition. Whether or not a TASI channel is allotted is indicated in A, B and C parts of the address (FIG. 7), each of which comprises one bit of the address corresponding to the trunk within the channel condition memory 8. Whether or not a TASI channel is allotted is determined by the binary indication l or If it is determined that the trunk for which there is a 0" indication, which indicates that there is an indication in the parts A, B and C that there is no allotment, and if the total number of trunks to which TASI channels are allotted is less than the total number n of TASI channels, said A, B and C parts corresponding to the trunk are immediately changed to 1 to indicate that there is an allotment.

If the total number of trunks arrives at the total number n of TASI channels, only the fact that the trunk requires the allotment ofa TASI channel is recorded. Another trunk to which a TASI channel has been allotted, but which is in the pose condition, is scanned or searched, and the indication is changed to O to indicate that there is no allotment. The trunk requiring the allotment is changed to 1 indicating that there is an allotment. The total number of trunks to which TASI channels are allotted is thus always maintained under the total number n of TASI channels by modifying the allotment of TASI channels corresponding to the voice condition.

In FIG. 8, the level discriminator is shown in greater detail. The level discriminator 5 comprises a level-comparing circuit 5a, a counting circuit 512, a frame-controlling circuit 5c, a TASI-allotting circuit 50' and a time control circuit'Se. The information stored in the buffer register 4 is read out to the level-comparing circuit 5a, which determines whether or not such information is above a specific level. The condition of a trunk is stored in the address position in the channel condition memory 8 exclusively corresponding to the trunk. The information of the D part of the address position corresponding to the trunk stored in the buffer register 4 is therefore read out via the buffer register 6. The counting circuit 5b provides the required addition in accordance with the result of the previous determination by the level comparing circuit 5a.

If, for example, the result is under a specific level, 1 is added to the information of the D part of the address. If the result is above a specific level, +2n is added to the information of the D part of the address. The result of the addition is again stored in the original position in the channel condition memory 8. If the result of the addition is positive, l is written in the D part of the address, and if said result is negative, 0 is written in said D part. This is repeated for all the trunks within one frame period and the timing of the process is determined by the control provided by the time control circuit 5e via the time signals 3. A negative addition result is immediately stored in the original position in the channel condition memory 8 via the writing buffer register 7. A positive addition result is transferred to the TASI-allotting circuit 5d.

The TASI-allotting circuit 511' comprises an allotting register in which the number of allotted channels is recorded and the contents of'the A, B and C part of the address indicating whether or not the channel is allotted corresponding to the trunk are read out together with the D part of the address and are transferred to said TASI-allotting circuit without passing through the counting circuit 5b. The channel is thus allotted to the trunk in accordance with the contents of the A, B and C part of the address, the result of the addition and the contents of the allotting register of the TASI allotting circuit 5d. That is, if there is an indication that a channel is allotted to the trunk which is being processed, the result of the addition is returned to the channel condition memory 8 via the writing buffer register 7 without modification. Even if it is not indicated that a channel is allotted, the result of the addition is similarly entered to the channel condition memory 8 via the writing buffer register 7 without modification, if the contents of the allotting register of the TASI-allotting circuit 5d equal the total number ofTASI channels.

If there is no indication of channel allotment, and the contents of the allotting register of the TASI-allotting circuit 5d are less than the total number n of the TASI channels, a channel is allotted to the trunk. That is, an indication of channel allotment is written in and is entered to the channel condition memory 8 via the writing buffer register 7. This processing is performed in each frame period, and when the result of the addition is positive, that is, the D part of the address is all l a request for speech is represented. When there is no indication of channel allotment, an allotment is awaited. The A, B and C parts of the address perform three types of operations, as hereinafter described. The TASI-allotting circuit 5d switches between the operations performed by the A, B and C parts of the address and the operation of copying the indicated information. The frame-controlling circuit 5c is controlled by the time control circuit 5e, which is initiated in operation by the time signals 3. The frame-controlling circuit 5 0 controls the timing of the burst to be transmitted by the station of the equipment, and informations of the A, B and C parts of the address are transferred from the TASI-allotting circuit 5d to the gate control circuit 12 and the TASI information adding circuit 13 at the control times, and the necessary control is thus provided.

The operation of the A, B and C parts of the address in indicating the condition of allotment of the TASI channels is as follows. In order to transmit voice informations continuously when TASI informations are transmitted by dividing them into a plurality offrarnes, it is necessary to transmit the TASI informations earlier than the voice informations controlled by said TASI informations by one signal frame, as hereinafter described, since all the TASI informations are received by the receiver after the reception of one signal frame. It thus becomes possible to control the transmitted voice informations by TASI informations transmitted one signal frame earlier. In other words, a TASI information transmitted with a voice information is a TASI information delayed by one signal frame.

It is therefore necessary to provide a memory for recording the TASI information being transmitted together with the voice information, that is, the TASI information in the transmission condition. It is also necessary to provide a memory for recording the TASI information already transmitted and controlling the transmission of the voice information being transmitted, that is, the TASI information in the operating condition. Furthermore, three types of memories are necessary, because in the memory for storing the TASI information in the transmission condition, the contents cannot be rewritten until all the TASI informations are transmitted to the other station, and in the memory for recording the TASI information in the operating condition, the voice informations transmitted to the receiver are controlled in accordance with the information recorded in said memory, so that the contents of the memory cannot be rewritten until the new TASI informations are all transmitted to the receiver, that is, until the end of the transmission of one signal frame.

For the foregoing reason, it is necessary to provide the third memory for determining the present condition of each trunk, that is, for determining whether each trunk is in the speech condition or the pose condition and recording such information for the succeeding control such as, for example, a memory for recording the TASI information in the rewriting condition. Therefore, in accordance with our invention, the memory for indicating the condition of allotment of the TASI channels is divided into the three bit positions A, B and C, shown in FIG. 8 and said three bit positions or parts are mutually utilized for periodically exchanging the functions. The

TASI informations comprise, for example, sampling periods or 25 frames, and in each period, each of the parts A, B and C is utilized in the same manner, that is, the mutual exchange of functions. The period is referred to as one signal frame. This is illustrated in FIG. 9.

In FIG. 9, D-ST is the memory of the channel condition memory 8 for storing TASI information in the rewriting condition. SGT-ST is the memory of the channel condition memory 8 for storing the TASI information in the operating condition. In a specific signal frame, for example, in a signal frame which is in time position 1, the condition of allotment of TASI channels is changed in accordance with the rewriting process hereinbefore described in the memory A which is utilized as the memory D-ST of the channel condition memory 8. In the same signal frame, the memory C, which was in the memory frequent changes of the indication of condition around the threshold value.

FIG. 10 shows a receiver. The receiver of FIG. 10 includes the voice information memory 53, the channel condition memory 58 and the related components of the station B of the communication system of our invention, as shown in FIG. 4. In FIG. 10, signals 50 are voice informations and TASI informations received from another station of the system. The TASI informations are coded to increase their reliability. When the TASI informations are decoded, whether or not a TASI channel is allotted to an arbitrary trunk is indicated in the bit position corresponding to such trunk. If a TASI channel is allotted, the number of such TASI channels may be derived from the fact that the TASI channel is arranged in accordance with the order of the trunk to which said TASI channel is allotted.

Signals 51 indicate that the PCM signals of the received TASI channels rearranged in the order of the trunks 27-1, 27- 2, 27-m of the station B corresponding to the trunks 17-1, 17-2, l7-m, respectively, are applied and that when there is no talking or voice transmission, PCM signals are applied at the PCM demodulator 60 to the trunk of the station B corresponding to the trunk of the station A to which no TASI channel is allotted. Signals 59 are the synchronizing signals from the PCM transmission line and function as the timing or time control signals to provide the timing for receiving the TASI informations and voice informations of the TASI chan- D-ST in the preceding signal frame, is utilized as the memory SGT-ST. In the same signal frame, the memory B, which was utilized in the memory SGT-ST in the preceding signal frame, is utilized as the memory SP-ST.

When a specific memory A, B or C is switched from SF-ST to D-ST, the contents of the memory indicate the condition of allotment determined two signal frames before, and only the part in which the allotment is changed is rewritten. The contents are therefore obviously unsuitable as indicative of the initial condition of D-ST. For this reason, the first frame of D-ST includes the operation of copying the contents ofa memory in which rewriting has just been completed and which is switched to SGT-ST as the initial condition. By completing this operation, it becomes possible to provide continuity to the right of priority of the channel to which the TASI channel has once been allotted.

When the memory in D-ST is rewritten, the threshold value utilized for the change from the pose condition to the speech condition is higher than the threshold value utilized for the change from the speech condition to the pose condition, out of threshold values relating to the counting value of the D part of the address. By providing different threshold values to the aforedescribed increase and decrease, it is possible to avoid nels and the timing for applying the rearranged received PCM signals to the PCM demodulator synchronously with the PCM transmitter.

in FIG. 10, the voice information memory 53 stores or records the voice informations in one frame and has addresses equal in number to theTASI channels. Writing into the voice information memory 53 is via a writing buffer memory 52 and readout from said voice information memory is via a reading buffer memory 54. A separating and compiling circuit 55 includes a decoding circuit for extracting TASI informations for the burst received at the station and determining from the error-correcting code whether or not there is error in the received TASI information. The decoding circuit of the separating and compiling circuit 55 also extracts TASI informations from which the error-correcting code has been removed. A discriminator 57 is connected to the output of the separating and compiling circuit 55 and is coupled to the voice information memory 53 via a gate control circuit 56. The discriminator 57 includes a counter for counting in each frame the number of frames constituting one signal frame. The counter of the discriminator 57 supervises to ensure that the synchronizing signal of the TASI control signal is always received at a specific constant value of said counter and fits the signal to the received synchronizing signals when the synchronism is shifted. The discriminator 57 writes the TASI informations provided by the separating and compiling circuit 55 into a channel condition memory 58, and also exchanges the functions of memories E and F of said channel condition memory 58. 4

When the voice informations and TASI informations are received via the signals 50, the voice informations, excluding the TASI informations, are written in succession into the voice information memory 53 via the writing buffer memory 52 commencing with the foremost channel, that is, the head of the voice informations. The TASI informations are separated and compiled by the separating and compiling circuit 55 and the available TASI informations are determined by the discriminator 57. Thus, TASI informations are provided at the output of the separating and compiling circuit 55. The bits corresponding to the trunks indicate whether or not the TASI channels are allotted to the channels, and the discriminator 57 records such indications in the channel condition memory 58 in unchanged order.

When TASI informations are transmitted by dividing them, if the receiver controls the reception of such TASI informations, such reception is controlled on the basis of incomplete TASI informations and there is confusion in the communication system. The transmitter must therefore transmit all of the TASI informations utilized for the control of reception before such TASI informations are utilized to control the reception. For this reason the TASI informations transmitted by being provided ahead of the voice informations are for the control of the voice informations of the next-transmitted signal frame. When the transmission of the TASI control signals is completed, the next-succeeding control signals are immediately transmitted.

Therefore, in order to control reception continuously at the receiver, it is necessary, in accordance with our invention to provide two memories. One memory is for storing or recording TASl'informations utilized for the control of the received voice informations, that is, TASI informations in operating condition, and a memory for storing or recording TASI informations utilized for controlling the next-succeeding signal frame, that is, TASI informations in the receiving condition. The memories E and F are thus provided in the channel condition memory 58. Each of the memories E and F comprises one bit corresponding to each trunk, as shown in FIG. 11. The memories E and F, as shown in FIG. I] perform the two functions of SGR-ST, which is the memory for storing the TASI informations in the receiving condition, and SP-ST, which is memory for storing the TASI informations in the operating condition, alternating under the control of the discriminator 57 (FIG. The switching between the functions of the memories E and F of the channel condition memory 58 is in complete synchronism with the switching of the transmitter memories.

Thus, the memory E is utilized as SGR-ST in a specific signal frame. The memory E in a signal frame in the time position I (FIG. 11) becomes SP-ST in the next signal frame. Therefore, while TASI informations are written in the memory in SGR-ST, the C memory of the channel condition memory controls the readout of the voice information memory 53 in SP-ST. Whether or not a TASI channel is allotted to a trunk is indicated in one bit in the address exclusively corresponding to such trunk. Only as to the trunk to which a TASI channel is allotted, +1 is added to the contents of the address, whereby the contents of the voice information memory 53 are successively read out and transmitted to the PCM decoder 60 (not shown in FIG. 10) via the reading buffer memory 54.

There is no readout from the voice information memory 53 to the trunk for which there is no indication of readout. Instead, a PCM signal pattern during nonconnection is trans mitted from a circuit component not shown in FIG. 10. As hereinbefore described, and in accordance with our invention, the functions of the memories A, B, C, E and F (FIGS. 8 and 10) are periodically exchanged, and in the memory which stores the TASI informations, one bit is provided for each trunk. The TASI control may therefore be realized with simple memories and with economy.

Each of the blocks of each of FIGS. 4, 5, 7, 8 and 10 comprises any suitable circuit arrangement for providing the operation ascribed thereto.

While the invention has been described by means of specific examples and in specific embodiments, we do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

We claim:

1. .A time-assignment speech-interpolation control system having a transmitter comprising discriminating means for determining the voice condition of each trunk of a voice communication system by determining if said voice condition transmitted via each trunk exceeds a specific level and allotting a time-assignment speech-interpolation system channel to each trunk which exceeds the specific level, said discriminating means comprising level-comparing means for determining whether the transmission data supplied from the trunks exceeds the specific level;

input means connected to said discriminating means for supplying thereto information from the trunks of a voice communication system having a plurality of trunks;

a channel condition memory coupled to said discriminating means for recording time-assignment speech-interpolation informations indicating the corresponding relationship between trunks and time-assignment speech-interpolation channels determined by said discriminating means, said channel condition memory comprising a first memory unit for storing the result of the determination of the level-comparing means of the discriminating means by comparison with data from corresponding trunks and a second memory unit for storing data indicating whether time assignment speech interpolation information may be allotted, said discriminating means further comprising time-assignment speech-interpolation allotting means for allocating time-assignment speech-interpolation information in accordance with the data stored in the first memory unit;

a voice information memory coupled to said discriminating means and said input means for storing voice informations supplied from the trunks to which time-assignment speech-interpolation channels are allotted from said voice informations in the order of the time-assignment speech-interpolation channels in accordance with the time-assignment speech-interpolation informations stored in said channel condition memory; and

time-assignment speech-interpolation information-adding circuit means connected to said discriminating means for adding time-assignment speech-interpolation informations stored in the second memory unit of said channel condition memory to voice informations stored in said voice information memory and transmitting the informations, said channel condition memory including a memory for storing the time-assignment speech-interpolation informations controlling the voice informations being transmitted, a memory for storing the time-assignment speech-interpolation informations transmitted by being added to the voice informations and a memory for storing the time-assignment speech-interpolation informations.

2. A time-assignment speech-interpolation control system as claimed in claim 1, further comprising means for dividing the time-assignment speech-interpolation informations into a plurality of frames and transmitting the divided informations.

3. A time-assignment speech-interpolation control system as claimed in claim 1, wherein the second memory unit of said channel condition memory stores one bit corresponding to the trunks.

4. A time-assignment speech-interpolation control system as claimed in claim 1, further comprising means for converting the time-assignment speech-interpolation informations to an information train of binary signals indicating if the time-assignment speech-interpolation channels are allotted to bit positions corresponding to the trunks and transmitting said binary signals.

5. A time-assignment speech-interpolation control system as claimed in claim 1, further comprising a receiver having a separating and compiling circuit for deriving time-assignment speech-interpolation informations from a received burst, input means connected to said separating and compiling circuit for supplying a received burst to said separating and compiling circuit, a voice information memory coupled to said input means for storing voice informations directed to said receiver, and a channel condition memory coupled to said separating and compiling circuit and to said voice information memory for storing time-assignment speech-interpolation informations provided by said separating and compiling circuit to read out the voice informations stored in said voice information memory corresponding to the trunks, said channel condition memory including a pair of memories each of which is alternately utilized as a memory for storing the time-assignment speech-interpolation informations for controlling the voice informations being read out and a memory for storing the timeassignment speechlinterpolation informations being transmitted to said receiver.

6. A time-assignment speech-interpolation control system as claimed in claim 5, wherein each of the pair of memories of said channel condition memory has addresses corresponding to the trunks and one bit which indicates whether time-assignment speech-interpolation information is allocated to a corresponding trunk and is stored in each of said addresses.

7. A time-assignment speech-interpolation control system as claimed in claim 1, wherein the second memory unit of the channel condition memory comprises three memory units corresponding to the respective trunks for storing information of corresponding trunks with the data indicating whether timeassignment speech-interpolation information may be allotted, one of the memory units storing the information of the trunk in which voice information is transmitted, another of the memory units storing the information of the trunk in which the voice signal is added in transmission and the third of the memory units storing the information of the trunk corresponding to the allotting of time-assignment speech-interpolation information, the three memories being utilized in cycles. 

1. A time-assignment speech-interpolation control system having a transmitter comprising discriminating means for determining the voice condition of each trunk of a voice communication system by determining if said voice condition transmitted via each trunk exceeds a specific level and allotting a time-assignment speech-interpolation system channel to each trunk which exceeds the specific level, said discriminating means comprising level-comparing means for determining whether the transmission data supplied from the trunks exceeds the specific level; input means connected to said discriminating means for supplying thereto information from the trunks of a voice communication system having a plurality of trunks; a channel condition memory coupled to said discriminating means for recording time-assignment speech-interpolation informations indicating the corresponding relationship between trunks and time-assignment speech-interpolation channels determined by said discriminating means, said channel condition memory comprising a first memory unit for storing the result of the determination of the level-comparing means of the discriminating means by comparison with data from corresponding trunks and a second memory unit for storing data indicating whether time assignment speech interpolation information may be allotted, said discriminating means further comprising timeassignment speech-interpolation allotting means for allocating time-assignment speech-interpolation information in accordance with the data stored in the first memory unit; a voice information memory coupled to said discriminating means and said input means for storing voice informations supplied from the trunks to which time-assignment speech-interpolation channels are allotted from said voice informations in the order of the time-assignment speech-interpolation channels in accordance with the time-assignment speech-interpolation informations stored in said channel condition memory; and time-assignment speech-interpolation information-adding circuit means connected to said discriminating means for adding timeassignment speech-interpolation informations stored in the second memory unit of said channel condition memory to voice informations stored in said voice information memory and transmitting the informations, said channel condition memory including a memory for storing the time-assignment speechinterpolation informations controlling the voice informations being transmitted, a memory for storing the time-assignment speech-interpolation informations transmitted by being added to the voice informations and a memory for storing the timeassignment speech-interpolation informations.
 2. A time-assignment speech-interpolation control system as claimed in claim 1, further comprising means for dividing the time-assignment speech-interpolation informations into a plurality of frames and transmitting the divided informations.
 3. A time-assignment speech-interpolation control system as claimed in claim 1, wherein the second memory unit of said channel condition memory stores one bit corresponding to the trunks.
 4. A time-assignment speech-interpolation control sysTem as claimed in claim 1, further comprising means for converting the time-assignment speech-interpolation informations to an information train of binary signals indicating if the time-assignment speech-interpolation channels are allotted to bit positions corresponding to the trunks and transmitting said binary signals.
 5. A time-assignment speech-interpolation control system as claimed in claim 1, further comprising a receiver having a separating and compiling circuit for deriving time-assignment speech-interpolation informations from a received burst, input means connected to said separating and compiling circuit for supplying a received burst to said separating and compiling circuit, a voice information memory coupled to said input means for storing voice informations directed to said receiver, and a channel condition memory coupled to said separating and compiling circuit and to said voice information memory for storing time-assignment speech-interpolation informations provided by said separating and compiling circuit to read out the voice informations stored in said voice information memory corresponding to the trunks, said channel condition memory including a pair of memories each of which is alternately utilized as a memory for storing the time-assignment speech-interpolation informations for controlling the voice informations being read out and a memory for storing the time-assignment speech-interpolation informations being transmitted to said receiver.
 6. A time-assignment speech-interpolation control system as claimed in claim 5, wherein each of the pair of memories of said channel condition memory has addresses corresponding to the trunks and one bit which indicates whether time-assignment speech-interpolation information is allocated to a corresponding trunk and is stored in each of said addresses.
 7. A time-assignment speech-interpolation control system as claimed in claim 1, wherein the second memory unit of the channel condition memory comprises three memory units corresponding to the respective trunks for storing information of corresponding trunks with the data indicating whether time-assignment speech-interpolation information may be allotted, one of the memory units storing the information of the trunk in which voice information is transmitted, another of the memory units storing the information of the trunk in which the voice signal is added in transmission and the third of the memory units storing the information of the trunk corresponding to the allotting of time-assignment speech-interpolation information, the three memories being utilized in cycles. 